The present invention relates to injectors for injecting fuel in the fluid state, and in particular in the liquid state, and designed to inject the fuel directly into a combustion chamber of a controlled ignition engine. It is particularly applicable to injecting gasoline, but it can also be adapted to other liquid fuels, such as alcohol-based fuels, and liquefied petroleum gas.
Direct injection injectors are already known comprising an injector body containing a needle that is axially movable by electrical control means (often constituted by a coil) and terminated by a shutter element, often of hemispherical shape, that co-operates with a seat for passing fuel. The needle is movable between a first axial position in which the shutter element bears against the seat, and a position in which it is spaced apart therefrom.
The stresses imposed on the injector for direct injection are much greater than those imposed for indirect injection into the manifold. It is necessary simultaneously to limit the penetration depth of the fuel jet, e.g. to avoid wetting the walls of the chamber, and to provide mixing between air and fuel that is as intimate as possible for better combustion, and to do this even though the time available for injecting fuel is very short.
To achieve this result, attempts have already been made to impart turbulent motion to the fuel.
Patent application FR 98/00554 describes an injector having a chamber for putting the fuel into rotation about the axis of the shutter element, which chamber is situated upstream from the seat and is defined between a plurality of elements.